Oxidization-active metals such as pure titanium and titanium alloy materials consisting mainly of titanium exhibit high heat resistance, excel in such mechanical properties as toughness and wear resistance, and being highly biocompatible, do not harm living organisms in which they are embedded. They therefore have the potential for extensive utility not only in industry but also in dental prosthetics, plastic surgery and other such surgical and medical fields.
However, since titanium materials are very active and are therefore exceedingly difficult to work, it has only been possible to process them in vacuo using special equipment and techniques. Because of this, it has not been possible to fabricate dentures and other complex, intricate articles from titanium.
JP-B 56-1981, for example, discloses that oxidization and other qualitative changes in a metal are prevented by maintaining an inert gas atmosphere in the melting chamber and the casting chamber from before the metal is melted until after it is cast. JP-B 56-1981 further discloses that the running of the metal is improved by causing the inert gas to pass under a differential pressure from the melting chamber through a gap passage, a passage hole, the sprue of the mold and the shaped cavity into the casting chamber so that at the time the metal is poured into the mold after being completely melted the molten metal flows smoothly into the deep regions of the shaped cavity of the mold as entrained by the inert gas flow.
The present invention proposes a method for non-oxidize casting of oxidization-active metal in which the absolute amount of oxygen is reduced to an ultra-low level by drying the mold.